The present invention relates to a method to provide a medium voltage interconnection for realizing an electrical connection between a receiving connector of a first equipment station and a receiving connector of a second equipment station.
Such an interconnection is generally known in the art. It is made of a metal conductor at the ends of which are mounted electrical connectors. The electrical connector mates with the receiving connector generally forming part of a xe2x80x9cbushingxe2x80x9d of an equipment station. The equipment station is typically a transformer or switchgear in transformation station and the properties of the connectors are therefore preferably standardized.
The electrical connector is molded in polyethylene material so as to form a massive conductive core enclosed within a screened insulating body. As a result, the interconnection is relatively rigid and, additionally, is not available in different relative short lengths, e.g. of about 30 cm.
A connector of this kind is described e.g. in FR-2 741 484. This document is directed to an electrical connector for connecting e.g. two cables, and comprising a conductive core including a metal conductor with at each end thereof, an electrical connector. It also comprises an elastic protective sleeve made of a layer of semiconductive or conductive rubber. This connector is pre-fabricated by molding a one-piece element.
An object of the present invention is to provide an interconnection of the above known type but of which the electrical connectors are relatively more flexible, and available in different lengths without any significant extra-cost.
According to the invention, this object is achieved by a method which comprises the steps of:
providing an electrical connector mating said receiving connector at each end of a metal conductor, said metal conductor with its two connectors forming a conductive core,
providing a flexible tube made of at least an insulating layer of elastomeric material and having the same length as said conductive core,
expanding radially said flexible tube and sliding therein said conductive core, and
releasing said flexible tube over said conductive core.
In this way, the molding process is replaced by an extrusion process. As a result, the conductive core is composed of a flexible conductor connected to two electrical connectors, whole enclosed within an elastic tube or sleeve to define connection insulated interfaces to mating the receiving connectors of the equipments. For many applications, flexible interconnections are more adequate due to the flexibility of material and dimensions.
The method of the present invention preferably comprises the steps of providing said electrical connector with a substantially conical shape of which the base has a diameter relatively larger than the diameter of said metal conductor, and of connecting said base to an end of said metal conductor.
The so obtained interconnection best matches the standard bushings.
More particularly, the present method further comprises the step of engaging one end of said flexible tube into an inner side of a conical bushing means made of insulating material and provided with said receiving connector so as to bring the electrical connector of the conductive core into contact with said receiving connector and said insulating layer of said flexible tube into contact with said inner side of said bushing means.
In a preferred embodiment, said method comprises the steps of providing said flexible tube with, coaxially starting from the center:
a first semiconductive layer,
an insulating layer made of elastomeric material, and
a second semiconductive layer.
Such an extruded 3-layer tube gives the best results with respect to flexibility and insulation properties.
Also in a preferred embodiment, said method further comprises the steps of:
providing an external locking ring onto at least one electrical connector of said conductive core, and
providing into said flexible tube at least one internal ring groove for receiving the locking ring of said electrical connectors when the tube is released over said conductive core.
The flexible tube or sleeve is then locked onto the electrical connectors or end-pieces of the conductive core to prevent any relative movement. The grooves may also be used to hold slidable outer clamps to mechanically clamp each electrical connector and possibly to achieve the external screening continuity between the interconnection and the mating parts.
The present invention also relates to a medium voltage interconnection obtained by the method of the invention and adapted to electrically connect a receiving connector of a first equipment station and a receiving connector of a second equipment station.
This medium voltage interconnection comprises a conductive core including a metal conductor with, at each end thereof, an electrical connector adapted to mate said receiving connector, and a flexible tube having at least an insulating layer made of elastomeric material and covering the whole conductive core.
In a characterizing embodiment of the present invention, said elastomeric material is a synthetic terpolymer of ethylene, propylene and diene [EPDM].
In a variant, said elastomeric material is a silicone.
These materials are preferred for their good flexibility and insulation qualities.
Further characterizing embodiments of the present method and medium voltage interconnection are mentioned in the appended claims.
It is to be noticed that the term xe2x80x98comprisingxe2x80x99, used in the claims, should not be interpreted as being limitative to the means listed thereafter. Thus, the scope of the expression xe2x80x98a device comprising means A and Bxe2x80x99 should not be limited to devices consisting only of components A and B. It means that with respect to the present invention, the only relevant components of the device are A and B.
Similarly, it is to be noticed that the term xe2x80x98coupledxe2x80x99, also used in the claims, should not be interpreted as being limitative to direct connections only. Thus, the scope of the expression xe2x80x98a device A coupled to a device Bxe2x80x99 should not be limited to devices or systems wherein an output of device A is directly connected to an input of device B. It means that there exists a path between an output of A and an input of B which may be a path including other devices or means.